|Function ||Transportation of food and nutrients such as sugar and amino acids from leaves to storage organs and growing parts of plant. This movement of substances is called translocation.
||Water and mineral transport from roots to aerial parts of the plant.
|Movement ||Bidirectional (Moves up or down the plant's stem from "source to sink")
||Unidirectional (Moves up the plant's stem)
|Occurrence ||Roots, stems and leaves. transports sucrose to growth (roots and shoots) and storage regions of the plant (seeds fruit and swollen roots)
||Roots, stems and leaves
|Additional Functions ||Forms vascular bundles with xylem
||Forms vascular bundles with phloem and gives mechanical strength to plant due to presence of lignin cells. The lignified secondary wall also makes the xylem waterproof and prevent it from collapsing under the pressure of water transpiration
|Structure ||Elongated, tubular shape with thin walled sieve tubes. The sieve tubes have pores at each end in the cross walls and microtubules that extend between sieve elements allowing longitudinal flow of material.
||Tubular shape with no cross walls which allows a continuous column of water + facilitates more rapid transport within the xylem vessels. There are two types - protoxylem (first formed xylem) + metaxylem (mature xylem) depending on pattern of lignin.
|Elements ||Sieve tubes, companion cells, phloem parenchyma (loosely packed resulting in intercellular spaces which allows gas exchange), bast fibers, intermediary cells,
||Tracheids, vessel elements, xylem parenchyma (loosely packed resulting in intercellular spaces which allows gas exchange), xylem sclerenchyma
|Nature of tissue ||Living tissue with little cytoplasm but no nucleus/tonoplast.
||Dead tissue at maturity so it is hollow with no cell contents
|Shape ||Phloem is not star shaped.
||Xylem is star shaped.
|Location in vascular bundle ||Phloem occur on outer side of the vascular bundle.
||Xylem occupies the center of the vascular bundle.